1. Field of the Invention
The invention relates to continuous production of foam material and more particularly to an apparatus which produces substantially flat top foam materials of different widths.
2. Description of the Prior Art
Foam sheets have been made from a liquid polyurethane foaming material spread on a continuously moving channel-shaped conveyor. The problem encountered with this type of apparatus is that the side fences of the conveyor cause a downward drag on the rising foam, resulting in a convexly curved top on the sheet. For most uses of the foam, such as for furniture, the tops have to be flat to produce a desired seating surface. Most often the convexly shaped tops were cut to a flat top and the removed material was scraped.
Side fences have been developed which not only move with the bottom conveyor but also move upwardly with respect to the bottom conveyor where the foam rises to lessen or eliminate any downward drag caused by the side fence. Such side fence mechanisms are disclosed in U.S. Pat. No. 3,325,823 issued to Boone on June 13, 1967, and U.S. Pat. No. 3,091,811 issued to Hackert on June 4, 1963.
These devices are limited to a variety of foaming materials which can be used, since different foaming materials have different foaming rates. If the foaming rate is too fast, the drag is not eliminated and if the foaming rate is not fast enough, the side fences could cause upward drag, resulting in a concave top surface, a feature as undesirable as the convex top.
The sloped portion of the conveyor has to have its slope adjustable. U.S. Pat. No. 3,832,099 issued to Berg on Aug. 27, 1974 discloses a vertically adjustable section of the bottom conveyor.
The apparatus using a sloped bottom conveyor and upwardly inclined side conveyor adequately produce flat top foam blocks which can be cut to whatever desired length after the foaming is completed. However, if narrower foam blocks are desired, the foam blocks have to be sheared to form the narrower foam block. The cutting creates a waste of foam plus an extra process in making the final foam block.